30 mm FOV Zoom Lens Configuration: Reverse Selection

A 30 mm inspection area, a 2/3" camera already chosen, no lens yet — this page works backwards from the field of view to the hardware that produces it.

You Know Your Part Is 30 mm Wide. Now What?

A drawing gives you a 30 mm inspection area, the camera is a 2/3" model already on the bracket, and the lens is the only open item. That is reverse selection — the field of view is the input, the hardware is the output.

Two habits make it harder than it is. Shopping by magnification compares bare bodies at "0.3X". Shopping by working distance picks the longest standoff and assumes the FOV will follow. Neither works: 30 mm on a 2/3" sensor is a wide request, and wide framing is the one direction a machine vision zoom body is not built for.

Starting from a working distance or a camera instead of a FOV? The four-path configuration guide is the better entry point.

The Three-Line Math: FOV to Magnification

Three lines, then this page stops doing arithmetic:

• Effective magnification = zoom body magnification × auxiliary objective factor × TV tube factor.
• HFOV = sensor width divided by effective magnification.
• For a 30 mm target on a 2/3" sensor (8.8 mm wide), magnification ≈ 8.8 ÷ 30 ≈ 0.29X (calculated).

That 0.29X is the whole optical specification; what remains is hardware. Derivations, other sensor formats and live arithmetic are on the magnification and FOV calculator walkthrough and the FOV calculator tool.

Why No Bare Zoom Body Reaches 30 mm on a 2/3" Sensor

A 6.5:1 or 12.5:1 ratio describes how far magnification travels, not how wide it opens. Every POMEAS body bottoms out well above 0.29X, so its widest framing is far narrower than 30 mm.

The 12.5X stops at 15.2 mm on 2/3", about half of what you need; even the 4K body on a larger 1" sensor reaches only 18.8 mm. ("14X" is a zoom ratio, not a magnification, and it does not help here.)

So every real answer takes the same shape: cut magnification by half, then choose where in the stack to cut it. In front of the body, an auxiliary objective changes magnification and working distance. Behind it, a TV tube changes magnification only and leaves working distance untouched. That is why a 0.5X appears in all three routes below — half is what the arithmetic asks for.

Route A — 12.5X Body + 0.5X Auxiliary Objective (155 mm WD)

A 0.5X auxiliary objective (SKU 75205) on the front, a 1X TV tube (75110) behind. The body is the PMS-LZL-12101 12.5X coaxial continuous zoom lens, with coaxial illumination as standard — an advantage that grows with standoff, because a ring light loses intensity with distance.

The result is 0.29X–3.75X, 30.3 mm down to 2.3 mm horizontally and 22.8 mm down to 1.8 mm vertically, calculated on the 8.8 × 6.6 mm sensor. Thirty millimetres sits at the wide end: the part fills the frame at minimum zoom, with the full 12.5:1 travel left for inspecting inside it. Swap the TV tube to 0.5X and the same 155 mm stack frames 60.7 mm; swap to 2X and it frames 15.2 mm.

What the objective buys. Working distance is locked at 155 mm — it does not move when you zoom, nor when you swap TV tubes. The defining property of an auxiliary objective is that it relocates the front focal point, so the whole system stands off farther — the principle behind what an auxiliary lens actually changes. In practice 155 mm is the difference between a ring light that fits around the lens and one that collides with it.

What it costs. Glass: elements and air-glass surfaces ahead of the body mean a longer stack, one more alignment interface, slightly less light at the sensor. Sampling: at 30 mm framing the pair works at 0.29X, half the bare body's minimum, so each pixel covers twice as much object (calculated, sampling roughly doubling to about 26 µm). Light: a ring or bar light at 155 mm delivers less on target, so exposure or output must rise.

Why 155 mm is its own tier, and why the same FOV can be had at 297 mm, is on the how the 155 mm tier is built (12.5X + 0.5X).

Route B — 12.5X Body + 0.5X TV Tube (WD Stays 77.4 mm)

Route B cuts magnification in the same proportion on the other side: a 0.5X TV tube (75105) between body and camera, nothing on the front. The bare body runs 0.58X–7.5X at 77.4 ± 2 mm; halving behind the lens gives 0.29X–3.75X, 30.3 mm to 2.3 mm horizontally, 22.8 mm to 1.8 mm vertically (calculated). Side by side with Route A the optical column is identical, digit for digit.

What differs is where the lens sits. A TV tube is a camera adapter: it works on the image-side cone behind the last lens group and cannot move the object-side focal plane. Working distance stays at 77.4 mm, tolerance included — about 78 mm less standoff than Route A (calculated).

What Route B buys. The simplest stack: body, tube, camera. No front glass, no extra length ahead of the lens, no new alignment interface, and the envelope in front of the part is exactly what it was with the bare body, so a fixture laid out for a plain 12.5X still works. You also keep the full 12.5:1 travel with one adapter and no hardware change.

What it costs. Clearance, and only clearance — but it is real. 77.4 mm has to cover ring light, part height, probe and Z travel, with ±2 mm of body tolerance on top; on a moving stage that becomes a collision calculation.

Two secondary costs follow. Corners: the widest end is the lowest magnification, where corner illumination and vignetting are hardest, so verify brightness at 0.29X. DOF: the 12.5X family publishes no DOF per magnification, so nothing about the bare-body figure survives by assumption.

One detail works for both 12.5X routes: TV distortion — image-side distortion at the sensor — stays down to 0.001%, which is what makes a 30.3 mm frame a trustworthy 30.3 mm at the borders.

Route C — 4K 1" Body with 0.5X TV (Headroom for Growth)

Route C changes the body rather than the front optic. The PMS-LZH-7505W 4K industrial zoom lens runs 0.68X–5.0X at 80 mm on a 1" sensor, with published resolution of 10.17 µm at 0.68X improving to 2.8 µm, DOF 1.78–0.07 mm and NA 0.033–0.12. With a 0.5X TV tube behind it the effective range is 0.34X–2.5X: 37.6 mm to 5.1 mm horizontally, 28.2 mm to 3.8 mm vertically (calculated on the 12.8 × 9.6 mm sensor).

The character differs. On Routes A and B, 30 mm is the edge of the range: the part fills the frame and every adjustment zooms inward. On Route C it is an interior point, with the frame opening to 37.6 mm — margin for a fixture outline, for part-to-part drift on a conveyor, or for a fiducial — the reference mark the program locates the part by — that must stay in view.

What it costs. Four things:

• Body and camera, not adapter: the 12.5X accepts sensors up to 2/3" and a 1" sensor behind it vignettes, so a bigger camera on a 12.5X cannot reach these numbers — the image circle is the constraint (see the sensor and image circle matching rules).
• Sampling: with the 0.5X tube each pixel covers about twice as much object as on the bare 4K body at the same zoom position (calculated), spending part of the 4K line's finer resolution.
• DOF: the 1.78–0.07 mm DOF belongs to the bare body; combination DOF is not published and does not transfer across the tube.
• Ceiling: 37.6 mm is where this route stops, so a 60 mm part is out of reach however you set the zoom.

Route Comparison: Same 30 mm FOV, Different Physics

All three frame a 30 mm part on their own sensor. The table is the shortest honest summary; the paragraphs after it cover what a table cannot show.

Depth of field is absent on purpose. The 12.5X family publishes none per magnification, and combination DOF does not inherit from a base lens. Route C is the only one with a published envelope — 1.78–0.07 mm — and that describes the bare 4K body. If DOF rather than FOV is your binding constraint, examine the trade in the zoom versus fixed focal comparison.

Standoff is the only real divider between A and B. Their optics are the same number. A is front glass and about 78 mm more room; B is a bare nose and a tight fixture. Nothing about image quality separates them at this framing.

Route C's headroom costs top-end range. It narrows to 5.1 mm at maximum zoom while A and B reach 2.3 mm. If a 2 mm feature inside the 30 mm area matters, the 12.5X routes keep more magnification in reserve.

If the Part Grows to 60 mm or Shrinks to 15 mm Next Quarter

Field sizes move, and a configuration that only does 30 mm is how projects buy a second lens six months later.

Route A is the flexible one: the objective stays put and only the TV tube changes — one objective, three tubes, three field tiers, one working distance. Route B gives two tiers, 30.3 and 15.2 mm, because 0.5X is already the lowest TV factor. Route C is the opposite shape: widest single setting, hard ceiling at 37.6 mm.

If the 60 mm part also needs long standoff, none of the three is right: that is the 0.25X tier, which puts the 12.5X body at 297 mm and frames 60.7 mm with a 1X TV tube (calculated) — see the the 297 mm long-working-distance option. For a sweep from 10 mm down to 4 mm, the logic differs entirely: a 10–4 mm FOV worked case.

What 0.29X Actually Resolves

Magnification is not resolution, and at 0.29X the distinction stops being academic. Both 12.5X routes reach 30 mm framing by halving magnification, so each pixel covers twice as much object as with the bare body at the same zoom position. The published figures still describe the body; the sampling on the part changed underneath them.

Read that column as a limit, not a promise. A sampling interval near 26 µm puts features at that scale at the edge of what the system separates; contrast, lighting angle and surface finish decide the rest. A 30 mm frame is a survey view — right for finding a defect, locating a part or reading a datum, wrong for judging a 10 µm scratch. Zoom to 3.75X and the frame is 2.3 mm while the body's resolution improves to 3.05 µm from 4.5X.

One caution that belongs to every route on this page: no DOF is published per magnification, so never scale a bare-body figure across an objective or a TV tube.

Four Mistakes When Selecting by FOV Alone

1. Upgrading the camera to widen the field. A bigger sensor does not widen the frame if the image circle cannot cover it. Behind a 12.5X a 1" sensor vignettes; the field is capped by the lens, not the pixel count. If you truly need 1", the body changes too — that is Route C, not an upgrade.

2. Reading zoom ratio as FOV range. A 12.5:1 body does not start wide. Its widest framing on 2/3" is 15.2 mm (calculated) and zooming out cannot pass it. Ratio is travel, not reach.

3. Treating an auxiliary objective and a TV tube as interchangeable. Both halve magnification, so on paper they look like the same purchase. In hardware they differ on the axis that usually decides the project: an objective changes working distance, a TV tube never does. Choose the objective for clearance.

4. Specifying FOV with no sampling number beside it. "30 mm FOV" says nothing about whether the system sees what you care about. Two routes with identical FOV can differ in standoff, envelope, corner illumination and DOF behaviour — none of it visible in a data sheet headline, and the standoff side of that trade is exactly working distance versus depth of field.

FAQ: 30 mm FOV Questions

Which lens gives a 30 mm field of view?

Three stock configurations reach 30 mm horizontally: a 12.5X body with a 0.5X auxiliary objective and a 1X TV tube at 155 mm; the same body with a 0.5X TV tube at 77.4 mm; or the 4K 1" body with a 0.5X TV tube at 80 mm, where 30 mm sits inside a 37.6 to 5.1 mm span (calculated).

How do I convert a 30 mm FOV into a magnification requirement?

Divide the sensor width by the target field. On a 2/3" sensor that is 8.8 mm divided by 30 mm, roughly 0.29X (calculated). The full derivation and live arithmetic are on the magnification and FOV calculator page and the FOV calculator tool.

Can a bare zoom body reach 30 mm on a 2/3" sensor?

No. Each body is limited by its minimum magnification: the 6.5X stops at 12.6 mm, the 12.5X at 15.2 mm and the 14X at 16.0 mm on 2/3", all calculated. Reaching 30 mm means cutting magnification by half, with a 0.5X objective in front or a 0.5X TV tube behind.

Should I use a TV tube or an auxiliary objective?

Use a TV tube when 77.4 mm of standoff is enough: it halves magnification without touching working distance. Use an auxiliary objective when you need the 155 mm tier for lighting, probes or fixture clearance. Both give the same 30 mm framing, so the decision is clearance, not optics.

What working distance does each route give?

Route A gives 155 mm, set by the 0.5X objective and unchanged by zoom or TV tube swaps. Route B keeps the bare 12.5X figure of 77.4 mm plus or minus 2 mm. Route C uses the 4K body at 80 mm. All three frame 30 mm horizontally on their own sensors.

What if the part grows to 60 mm next quarter?

On Route A, swap the 1X TV tube for a 0.5X TV tube and the same 155 mm setup frames 60.7 mm (calculated). Route B cannot follow: 0.5X is already the lowest TV factor, so 30.3 mm is its ceiling. Route C stops at 37.6 mm.